CHEM 001C Lecture Notes - Lecture 13: Alkaline Battery, Redox, Lead
CHEM 001C Lecture 13: Electrochemistry
●Electrochemistry
○Oxidation: loss of electrons
○Reduction: gain of electrons
●Galvanic Cells
○Galvanic cells: separate oxidation and reduction half-reactions
■Can be harnessed to use electrical energy (batteries)
●Battery
○Battery: two electrochemical reactions are combined using external connections,
and in which electrical energy is generated
■Used in vehicles: reduce widespread emissions/ pollution
■Increase conversion efficiency of chemical energy to mechanical energy
●Lead-Acid Cell (Car Batteries)
○PbO2(s) + Pb(s) + 2H+
(aq) + 2HSO4
-
(aq) → 2PbSO4(s) + 2H2O(l)
■Solid precipitate (PbSO4(s)) sinks to the bottom of the cell
○Discharge: spontaneous release of electrons (redox reaction)
■Discharge potential for this reaction: +2.041 V
○Recharge: force electrical current in the reverse direction to regenerate reactants
●Dry Cell/ Alkaline Batteries
○Anode: Zn(s) + 2OH-
(aq) → ZnO(s) + H2O(l) + 2e-
○Cathode: 2MnO2(s) + H2O(l) + 2e- → Mn2O3(s) + 2OH-
(aq)
●Lithium Battery
○Used in small consumer devices (watches, calculators, etc.)
○Li(s) + MnO2(s) → LiMnO2(s)
●Large Scale/ Reusable Storage
○Dry cells/ alkaline batteries: primary cells
■Designed to be used once and discarded
○Reusable/ rechargeable batteries: secondary cells
Document Summary
Galvanic cells : separate oxidation and reduction half-reactions. Can be harnessed to use electrical energy (batteries) Battery : two electrochemical reactions are combined using external connections, and in which electrical energy is generated. Used in vehicles: reduce widespread emissions/ pollution. Increase conversion efficiency of chemical energy to mechanical energy. Pbo 2(s) + pb (s) + 2h + (aq) + 2hso 4 . Solid precipitate (pbso 4(s) ) sinks to the bottom of the cell. Discharge : spontaneous release of electrons (redox reaction) Discharge potential for this reaction: +2. 041 v. Recharge : force electrical current in the reverse direction to regenerate reactants. Anode : zn (s) + 2oh - (aq) zno (s) + h 2 o (l) + 2e - Cathode : 2mno 2(s) + h 2 o (l) + 2e - mn 2 o 3(s) + 2oh - (aq) Used in small consumer devices (watches, calculators, etc. ) Designed to be used once and discarded.
